1. Field of the Invention
The present invention relates to a cleaning apparatus for a fixing device used in an image forming apparatus such as a laser printer, electrophotographic apparatus, etc. to fix transfer paper having a toner image transferred thereto from the surface of an image retainer by means of a heat roller and a press roller.
2. Description of the Prior Art
In image forming apparatus utilizing electrostatic images, such as electrophotographic reproducing machines, electrostatic recording apparatus, etc., an electrostatic image is formed on an electrostatic image retainer and developed by applying a toner with a developing device to obtain a visible toner image, which is then transferred and fixed to transfer paper (recording paper), thereby obtaining a desired copy.
To fix the toner image to the recording paper, it is common to employ the thermal fixing method in which the toner is fused and thereby fixed to the recording paper by means of a heat roller. Since fixing is accompanied by the offset phenomenon that all the toner on the recording paper is not fixed thereto, but a part of it adheres to the peripheral surface of the heat roller, the roller needs to be cleaned. The cleaning of the heat roller has heretofore been effected by means of a cleaning roller, a cleaning web made of a non-woven fabric, etc.
The prior art that employs a cleaning roller involves the problem that, as the cleaning is repeatedly carried out, the cleaning roller itself gradually becomes stained. In the cleaning by means of a cleaning web made of non-woven fabric or the like, if the cleaning web is taken up by rotating a take-up shaft for a fixed time or through a fixed angle for each cleaning operation, the roll diameter of the take-up shaft gradually increases and consequently the amount of cleaning web fed for each cleaning operation also gradually increases, resulting in the cleaning web being fed more than is necessary. To overcome this problem, a method in which the amount of feed of the cleaning web is controlled by means of a pinch roller as in the case of a tape recorder (see Japanese Patent Laid-Open No. 58-182673) and another method in which the roll diameter of the take-up shaft is detected at all times to control the amount of cleaning web taken up (Japanese Patent Laid-Open No. 60-143374) have been proposed. These methods, however, involve the problems that the mechanism becomes complicated and costly due to necessity for a tension arm or a sensor and that the pinch roller or the sensor also become stained.